Exchange between Interlayer and Intralayer Exciton in WSe2/WS2 Heterostructure by Interlayer Coupling Engineering

Because of type-II band alignment, interlayer exciton (IX) is found in a van der Waals (vdW) heterostructure (HS) formed by two monolayers of transition-metal dichalcoge-nides. Manipulation of IXs is of great importance for excitonic integrated devices. Here, we demonstrate that high pressure and tensile strain can be applied to enhance and reduce interlayer coupling of WSe2/WS2 HS, respectively. High pressure induces the transform of intralayer excitons to IX, while tensile strain leads to the transform of IXs to intralayer excitons. In addition, there is a direct-to-indirect band gap transition of WSe2/WS2 HS. The interlayer distance of WSe2/WS2 HS is reduced under high pressure, but it increased under uniaxial tensile strain from first-principles calculations. The calculated band structures explain well the transformation between interlayer and intralayer excitons of WSe2/WS2 HS. This work demonstrates the exchange of interlayer and intralayer excitons and paves the way to manipulate excitons of HS for excitonic applications.

Automated summary

This study reveals the influence of high pressure and tensile strain on interlayer and intralayer excitons in the WSe2/WS2 heterostructure. High pressure can transform intralayer excitons to interlayer excitons, while tensile strain leads to the transformation of interlayer excitons to intralayer excitons.